The present invention broadly relates to an apparatus for connecting overlapping ends of thermoplastic band material or straps which have been stretched or tensioned around at least one package or article being wrapped by means of a separate tensioning device.
In its more particular aspects, the connection apparatus of the present invention comprises a base plate serving as a base or support for the apparatus on the package or article being wrapped. A predetermined gap is situated above the base plate and serves to accommodate the overlapping strap or band ends. Adjoining this predetermined gap are a welding jaw for frictional welding which is driven or actuated with a backward-and-forward motion or to-and-fro oscillation in a direction substantially transverse to the direction of the band or strap and a clamping surface situated opposite to this welding jaw.
Such an apparatus serves, together with a separate tensioning device, to wrap a package or article being wrapped or a number of articles which are to be wrapped. The tensioning device normally comprises a slotted wheel serving as the tension-producing or tensioning element. The uppermost end of the two overlapping ends of the band or strap is inserted into the slot of the slotted wheel and tensioned by turning or rotating the slotted wheel. In order to connect both strap or band ends together, the apparatus, with its slot opened laterally, is placed on a package or article being wrapped and moved laterally until both strap ends overlap one another in the slot. The connection of these overlapping strap or band ends is made by a frictional weld, whereby both ends are rubbed against one another until they fuse.
A known apparatus of the initially discussed type, as disclosed in British Pat. No. 2,055,685, published Mar. 11, 1981, is composed of a lower fixed or stationary welding jaw and an upper vibrating or to-and-fro oscillatingly driven friction jaw. The lower fixed welding jaw is formed by the base plate of the apparatus. To weld using this known apparatus, the upper welding jaw, which is pivotably mounted about an axis extending perpendicular to the plane of the welding jaws, is driven or actuated by an eccentric mechanism or cam. The shaft of this eccentric mechanism or cam is disposed substantially parallel to the plane of the welding jaws. With this arrangement the upper welding jaw engages with the uppermost strap or band end in order to vibrate or to move it back-and-forth in a direction substantially transverse relative to the lowermost strap or band end.
Actuation or drive problems are not encountered as long as sufficient power is available to actuate such an apparatus, for example, when power is supplied from an electric power supply network. In case such an apparatus is to be constructed, however, as a portable or hand-held unit, the dependence of its connection to a socket or outlet of an electric power supply network is a disadvantage. Although it is possible to dimension the drive mechanism of such an apparatus for battery operation by building a correspondingly large battery into the apparatus, the apparatus then becomes heavy and unwieldly so that the advantage with respect to an apparatus operated from an electric power supply network is at least partially lost.
Other known constructions of such type of equipment are exemplified by German Pat. No. 1,924,061, granted Jan. 7, 1971; German Pat. No. 1,704,048, granted Mar. 2, 1972; Swiss patent No. 494,632, granted Sept. 30, 1970; German Published Pat. No. 2,802,034, published June 13, 1979; French Published Pat. No. 2,122,891, granted Sept. 1, 1974; German patent publication No. 3,200,951, published Apr. 14, 1983, and Swiss Pat. No. 637,587, granted Aug. 15,1983.